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Join Date: May 2008
Posts: 1,701
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Slight Vibration - Flywheel Issue?
As I've been putting my 85.5 through its paces following a total engine reseal - I've begun to notice a few things. Among these is a slight, rythmic vibration, which I can both hear and feel through the gearshift knob. I notice this mostly in the range of 2500 rpm.
So I'm thinking...that this might be either a slightly out of balance flywheel, or a torque tube issue, possibly a tranny issue, and maybe something as simple as the P.S. pump pully at the end of the crank...which does seem to rotate slightly off center - but its mass does not seem large enough that it should cause anything noticeable. My first thought was maybe a balance shaft issue....but I don't think this is it. When I rescued this car several years ago and pulled the engine, I'd noticed that the P.O. had replaced the clutch as he mentioned, but he'd also left off the inspection cover and thus there was a slight amount of surface rust on the flywheel, which I very gently sanded with some 600 grit paper. Would this have been enough to throw the flywheel out of balance? I admit that I'd cheaped-out by not having the flywheel resurfaced and rebalanced - so maybe this is the culprit. If so...can anyone advise how much risk this might pose to the engine bearings? I'd hate to have an issue like this slowly wreck an otherwise very smooth engine. |
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10-14-2011, 04:25 AM
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Join Date: Sep 2011
Posts: 14
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I have a slight vibration also, but I am almost 100% sure mine is because of the TT bearings, they are making a terrible racket
 Haven't had the time to fix it! I think if your TT was going bad you would hear a slight noise.
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----------------------------------------------------- My cars : 1984 Porsche 944 1985 Nissan Pickup SBC swap 2005 Chevy cobalt |
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10-14-2011, 04:50 AM
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Proprietoristicly Refined
Join Date: Jul 2001
Location: ~Carefree Highway~
Posts: 5,833
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If you are certain it is not the balance shafts or pullys, bad engine mounts at 1100rpm, and the cam belt matches the timing marks perfectly (not off 1/2 tooth) ,,the sanding would not make a difference.
You can check the flywheel balance by revving the engine at certain RPMs in the garage in NEUTRAL. If you get the vibration standing still it will eliminate the TT torque tube bearings, If you want to check the torque tube for vibration, disconnect the rear transaxle coupler--slide it back. Start the car and shift to where you have felt the vibration. If you feel the vibration (or noise) in the shift lever now, it is probably the TT bearings. GL John
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1988 924S, 85,750K ..+ 1987 924S, 154K DD (+15K est. bad odo) |
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10-14-2011, 04:56 AM
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White and Nerdy
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Quote:
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Shadilay. |
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10-14-2011, 05:41 AM
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Proprietoristicly Refined
Join Date: Jul 2001
Location: ~Carefree Highway~
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Thanks,
You are right, In NEUTRAL with the clutch pedal pressed in. John
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1988 924S, 85,750K ..+ 1987 924S, 154K DD (+15K est. bad odo) |
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10-14-2011, 05:46 AM
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Join Date: Dec 2010
Location: LA, CA (Agoura Hills)
Posts: 244
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Wouldn't clutch pressed in while trans in gear while car is stationary ensure no TT spinning?
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10-14-2011, 09:27 AM
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Proprietoristicly Refined
Join Date: Jul 2001
Location: ~Carefree Highway~
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Yes, Good point.
Neutral would be safer----when stationary. I can mentally see someone frustrated and tired, Start the engine in the garage, Put car in gear, Press in the clutch pedal, When finished while the engine is running, Release the clutch before turning the engine off....  Thanks John
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1988 924S, 85,750K ..+ 1987 924S, 154K DD (+15K est. bad odo) |
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10-14-2011, 11:25 AM
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Registered
Join Date: Dec 2010
Location: LA, CA (Agoura Hills)
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10-14-2011, 12:07 PM
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Copenhagen Blue
